DEVELOPMENT OF THE ELASMOBRANCH LIVER 



341 



intestinal junction. The walls of these lateral diverticula are 

 of the same thickness as those of the dorsal zone, i.e., 25 to 30 ^x, 

 but the nuclei are somewhat more elongated and lie at the basal 

 ends of the cells, leaving a clear zone towards the lumen of the 

 gut. The boundaries of the cells are faintly distinguishable. 



- ->-/ 'v 



/:•• ;~\ s\ 





P-Arcb.g. 



Hcp.d. 



J^d-Tchq. 



Fig. 2 Transverse section of an embryo of 19 to 20 segments, 3.0 mm. in length 

 (K.U.E.C. 451). 0.06 mm. posterior to the anterior wall of the yolk stalk. X 100. 

 Hep.d., hepatic diverticulmn; P-arch.g., para-archenteric groove. 



Fig. 3 Tranverse section of an embryo of twenty-four segments, 3.6 mm. in 

 length (S.C. 14). 0.09 mm. posterior to the anterior wall of the yolk stalk. X 100. 

 Hcp.d., hepatic diverticulum; P-arch.g., para-archenteric groove. 



Above and below the diverticula the nuclei are broadly oval and 

 scattered through the thickness of the epithelium, and there are 

 no distinct cell outlines to be seen with ordinary stains. Figure 

 3 is a transverse sectfon of this embryo 90 /x behind the anterior 

 wall of the yolk-stalk. 



